KR20160057641A - Quantum dot and π-conjugated molecule hybrids nanoparticle, and molecular electronic devices including the same - Google Patents

Abstract

The present invention relates to a quantum dot-organic semiconductor hybrid nano structure which connects a functional organic semiconductor to a quantum dot, to a molecular electronic device comprising the same, and to a producing method of the nano structure and, more specifically, to a quantum dot-organic semiconductor hybrid nano structure which is a next generation n-p conjugated nano structure using energy and charge transfer phenomenon between an quantum dot which is an n-type semiconductor and a p-type organic semiconductor, to a producing method thereof, and to a molecular electronic device comprising the nano structure.

Description

Quantum dot-organic semiconductor hybrid nanostructures and molecular electronic devices containing the same are well known in the art, including quantum dots and π-conjugated molecule hybrids nanoparticles,

TECHNICAL FIELD The present invention relates to a quantum dot-organic semiconductor hybrid nanostructure in which a functional organic semiconductor is bonded to a quantum dot, a molecular electronic device including the nanostructure, and a method for producing the nanostructure, and more particularly, to a nanostructure providing new optical and electrical properties .

With the rapid development of advanced materials and device technologies, electronic or optical devices such as "wearable computers" and "flexible electronic newspapers" that have existed only in the imagination are realizing. Human-friendly optoelectronic devices are being studied and fabricated based on advanced materials with new properties.

In order to overcome the optical and electrical limitations of existing materials, hybrid nanostructured materials based on nanophysical theory show synergistic effects beyond the limitations of existing materials due to specific effects between materials. When a quantum dot having excellent luminescence characteristics and an organic semiconductor having a light-emitting and pie-conjugated structure having good conductivity are combined, there is a theoretical prediction that maximizes luminescence and electric characteristics through energy transfer and charge transfer between the two. However, Research has not been conducted.

Patent Document 1: Patent Document 10-2011-0117972 Patent Document 2: JP-A-10-2014-0006401 Patent Document 3: Japanese Patent Application Laid-Open No. 10-0095379 Patent Document 4: JP-A-10-2014-0043951 Patent Document 5: JP-A-10-2010-0086197 Patent Document 6: WO 2011/131280 Patent Document 7: WO 2012/119551

The present invention relates to a quantum dot-organic semiconductor hybrid nano structure which is a next generation np junction nanostructure based on the energy and charge transfer phenomenon between a quantum dot which is an n-type semiconductor and a p-type organic semiconductor, a method for producing the same, The present invention also provides a molecular electronic device comprising the same.

Quantum dots are zero-dimensional nanomaterials with diameters below tens of nanometers (nm). When quantum dots are formed by inorganic light emitting semiconductors, quantum confinement effect is observed in which the emission color changes depending on the size of the quantum dots. The distribution of the energy level and the characteristics of the emission wavelength are changed depending on the size, and the optical stability is obtained when the core-shell is fabricated. Therefore, semiconductor-based quantum dots can be applied to electronic devices, displays, and energy devices.

On the other hand, an organic semiconductor compound having a pie conjugate bond has an excellent electric conduction characteristic due to a structure in which electrons in a pie (π) orbit of a constituent carbon atom are alternately combined, and exhibits self-luminescence characteristics. OLED (organic light emitting device) light emitting material. Such a hybrid of a pi conjugated molecule and a quantum dot can be used as a novel material for a light emitting diode in a flexible display device. Hybrid materials with enhanced charge transfer efficiency can also be used as nanoscale photovoltaic devices.

Controlling the energy transfer and charge transfer efficiency between the quantum dot and the pi conjugated molecule can control the distance between the quantum dot and the pi conjugated molecule and the degree of superposition of the spectrum. Here, energy transfer refers to a phenomenon in which energy gap of a donor whose energy gap is slightly larger in the two molecules emitting light is transferred to an acceptor having a smaller energy gap. At this time, the overlap of the absorption spectrum of the acceptor with the emission spectrum of the donor should be good, which controls the degree of energy transfer by adjusting the distance between donor and acceptor molecules, and tends to be inversely proportional to the sixth power of distance. That is, when the critical distance for energy transfer is 1 to 10 nm, the quenching phenomenon disappears when the thickness is less than 1 nm, and the energy transmission is rarely performed when the distance is about 10 nm or more.

In addition, charge transfer refers to the phenomenon that the charge of an excited donor is directly transferred to another acceptor when the donor and acceptor molecules are located close to each other, and the electron orbit of the donor and the acceptor It is possible when overlapping, so it occurs when the distance between two substances is very close to 1 nm or less.

Using this phenomenon, the present invention provides a nanostructure comprising a quantum dot as a core layer and an organic semiconductive compound of a pi conjugated structure as a cell layer, thereby adjusting the distance between both materials, thereby providing a core material of a nano-sized molecular optoelectronic device .

In the nanostructure according to the present invention, since the quantum dot-polythiophene derivative compound has a direct bonding structure of the n-type and the p-type semiconductor, the increase of the photocurrent, in which electrons and holes generated by light are transmitted through the heterojunction, - By controlling the distance and structure between organic semiconductors, it is possible to provide an excellent effect to a device using a photovoltaic effect such as a solar cell.

Figure 1 shows the chemical structure of a nanostructure composed of a quantum dot-P3000 organic semiconductor compound.
Figure 2 shows a single QD-P3000 and some HR-TEM images.
Figure 3 shows the FT-IR spectrum of OA-bound green QD and hybrid QD-P3000 nanoparticles.
Figure 4 shows a normalized UV-vis absorption spectrum of P3000 and QD-P3000 and a solution photoluminescence (PL) spectrum of green QD.
5 shows a laser confocal microscope (LCM) emission spectrum of a QD-P3000 nanostructure in which a P3000 organic semiconductor is bonded to the surface of a green luminescent CdSe / ZnS quantum dot (the right inset shows a color CCD image in the case of only quantum dots) And a color CCD image of the QD-P3000 nanostructure (below)).
6 shows a transient absorption (time-resolved absorption) difference spectrum of QD-P3000 (λ _ex = 510 nm).
Figure 7 shows normalized time-resolved photoluminescence (PL) decay curves of green QD and QD-P3000 nanostructures.
8 shows a photoreaction current-voltage characteristic curve using a laser ( _ex = 488 nm) of a QD-P3000 single nanostructure.

In order to achieve the above object, the present invention provides a quantum dot-organic semiconductor hybrid nano structure having a core-shell structure in which a functional organic semiconductor is bonded to the surface of a quantum dot. The structure can control energy and charge transfer efficiency between quantum dots and organic semiconductors, thus providing new luminescence and electrical properties.

Conventional quantum dots have excellent luminescence characteristics, but display and solar cell materials have problems in mass production for control of physical properties and large area coating after synthesis. In addition, organic semiconductor light emitting materials used in OLEDs require improvement in optical properties.

In order to overcome these drawbacks, the present invention provides a nanostructure capable of controlling mutual luminescence characteristics by attaching functional groups to the ends of organic semiconductors so that quantum dots and organic semiconductors can be bonded well.

When the quantum dots and organic semiconductors are close to each other (less than 1 nm), the photocurrent increases due to the smooth charge transfer. As a result, It can be used as solar cell nano material or display material.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a nanostructure comprising a core layer made of quantum dots and a shell layer made of an organic semiconductor compound having a pi conjugated structure.

In a specific example of the present invention, the quantum dot is a combination of two species selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgTe, GaN, GaP, GaAs, InP, And a shell layer made of an organic semiconductor compound of a pi conjugated structure.

In another embodiment of the present invention, the quantum dot is selected from the group consisting of CdSe / ZnS, CdSe / ZnSe, CdS / ZnSe, CdS / ZnS, CdTe / ZnSe and CdTe / ZnS.

In another specific example of the present invention, the present invention provides a nanostructure characterized in that the organic semiconducting compound of the pi conjugated structure is represented by the following formula (1).

≪ Formula 1 >

은 코어층을 나타내고, R은 치환기로 치환되거나 치환되지 않은 C1-C20 알킬, 치환기로 치환되거나 치환되지 않은 C2-20 알케닐, 치환기로 치환되거나 치환되지 않은 C2-20 알키닐기, 치환기로 치환되거나 치환되지 않은 C1-20의 알콕시기, 또는 치환기로 치환되거나 치환되지 않은 C6-30의 아릴옥시기로 이루어진 그룹에서 선택되고, 상기 치환기는 C1-C20 알킬, 할로겐, C1-C20 알콕시, OH, 중수소로 이루어진 그룹에서 선택되며, n은 1 내지 20의 정수를 나타낸다). (In the formula 1,

Wherein R represents a core layer, R is C1-C20 alkyl optionally substituted with a substituent, C2-20 alkenyl optionally substituted with a substituent, C2-20 alkynyl optionally substituted with a substituent, An unsubstituted C1-20 alkoxy group or an unsubstituted C6-30 aryloxy group, and the substituent is selected from the group consisting of C1-C20 alkyl, halogen, C1-C20 alkoxy, OH, deuterium And n represents an integer of 1 to 20).

Preferably, in the above formula (1), R is a C1-C20 alkyl. Even more preferably, a nanostructure comprising a shell layer composed of an organic semiconductor compound of a pi-conjugated structure in which R is C5-C10 alkyl.

Another specific example of the present invention provides a nanostructure wherein the nanostructure has a diameter of 30 to 20 nm and a nanostructure wherein the nanostructure is an n-p junction type.

In a preferred specific example of the present invention, the core layer made of quantum dots is CdSe / ZnS, and the organic semiconductive compound having a pi conjugated structure is a compound wherein R is C ₈ H ₁₇ in the compound represented by the formula 1 Lt; / RTI > nanostructures.

In another specific example of the present invention, there is provided a molecular electronic device comprising a nanostructure including a core layer made of quantum dots and a shell layer made of an organic semiconductor compound of a pi conjugated structure, An electronic device including an electronic device is also provided. Here, the electronic device is preferably an electronic device including a solar cell, a display or a lighting device and a control unit for controlling the same.

The present invention also provides a compound represented by the following general formula (2) as the organic semiconductor compound.

(2)

(Wherein R is C1-C20 alkyl substituted with a substituent, C2-20 alkenyl optionally substituted with a substituent, C2-20 alkynyl optionally substituted with a substituent, C1- C20 alkyl, halogen, C1-C20 alkoxy, OH, deuterium, and the substituent is selected from the group consisting of halogen, C1-C20 alkoxy, , and n represents an integer of 1 to 20)

Accordingly, the present invention provides a method for providing the nanostructure,

a) fabricating core-shell quantum dots with two inorganic semiconductor materials;

b) chemically synthesizing the P-type conjugated organic semiconductor compound;

c) introducing a functional group into the terminal of the organic semiconductor compound;

and d) introducing the compound into the surface of a quantum dot. The present invention also provides a method for producing a nanostructure comprising a quantum dot and an organic semiconductor compound core-shell layer.

Here, the compound of the step (c) is a compound represented by the formula (2).

In the step (d), a compound represented by Formula 2 is introduced into a quantum dot by an ultrasonic wave in a ligand exchange manner.

Hereinafter, embodiments of the present invention will be described in detail. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be apparent to those of ordinary skill in the art.

Example 1: Synthesis of CdSe-ZnS core-shell Green quantum dot

CdO (0.4 mmol), zinc acetate (4 mmol) and oleic acid (5.5 mL) are added to the reaction apparatus together with 1-octadecene (20 mL) and heated at 150 ° C. Oleic acid is substituted for zinc and a vacuum of 100 mTorr is applied for 20 minutes to remove acetic acid, which is an impurity. And when heat of 310 ℃ is applied, it becomes a mixture of transparent color. The one in which Se, S solution dissolving S powder in 0.1 mmol of Se powder and 4 mmol in 3 mL trioctylphosphine after maintained at 310 ℃ 20 minutes to _{Cd (OA) 2, Zn (} OA) reaction containing ₂ solution mechanism Immediately inject. The mixture was grown at 310 ° C for 10 minutes and then stopped by using an ice bath. Ethanol precipitate, and the quantum dots are separated using a centrifuge. The excess impurities are washed off with chloroform and ethanol.

FT-IR (NaCl pellet, cm ^-1 ): 2800-3000 (Alkane CH), 1617 (C = O)

Example 2 Synthesis of Thiophene-3-carbonyl chloride (3-TCCl)

5 g (0.04 mol) of thiophene-3-carboxylic acid (3-TCA) is added and vacuum dried. The dried 3-TCA was dissolved in 8 mL of methylene chloride under a nitrogen stream, cooled with ice-water bath, 6.7 mL (78 mmol) of oxalyl chloride was slowly added, and the temperature was slowly raised to room temperature for 24 hours . After completion of the reaction, remove the solvent used in the reaction and dissolve in 13 mL of methylene chloride.

Example 3: Synthesis of N, N-Diethylthiophene-3-carboxamid (3-TCDA)

Place the flask in an ice water bath, cool, and add 8.2 mL (78 mmol) of diethylamine and 12 mL of methylene chloride. The synthesized 3-TCCl solution was slowly added to the flask and reacted at room temperature for 30 minutes. The reaction mixture is extracted with dichloromethane and H ₂ O. The organic layer is dried over anhydrous MgSO ₄ and filtered under reduced pressure. The solvent was removed and vacuum distillation yielded 6 g (yield: 83%) of yellow liquid 3-TCCl.

_{^{1 H-NMR (CDCl 3,}} 300 Mhz): δ (ppm) = 7.48 (s, 1H), 7.32 (d, 1H), 7.20 (d, 1H), 3.41 (d, 1H), 1.19 (t, 6H )

Example 4 Synthesis of 4,8-Dihydrobenzo [1,2-b: 4,5-b '] dithiophene-4,8-dione (4,8-BDTO)

Add 2.5 mL (13.6 mmol) of 3-TCDA in 70 mL of tetrahydrofuran (THF) and cool with ice water bath. Add 8.52 mL (13.6 mmol) of n-BuLi to the cooled solution slowly and react at room temperature for 30 minutes. After the reaction, excess ice water is added and stirred for 4 hours, followed by filtration under reduced pressure. The filtered yellow material was washed with excess water, methanol, and hexane, and 2.1 g (yield: 71%) of yellow 4,8-BDTO was obtained.

_{^{1 H-NMR (CDCl 3,}} 300 Mhz): δ (ppm) = 7.70 (d, 2H), 7.65 (d, 2H)

Example 5 Synthesis of 4,8-Dioctyloxybenzo [1,2-b: 4,5-b '] dithiophene (DO-BDT)

Add 2 g (9.1 mmol) of 4,8-BDTO and 1.3 g (20 mmol) of zinc powder and add 28 mL of water. 5.45 g of NaOH is added thereto, and the mixture is refluxed at 120 ° C for one hour. When the color of the reaction changes from yellow to red to orange, 4.74 mL (27 mmol) of 1-bromo-octane and a small amount of tetrabutylammonium bromided are added and reacted for two hours. After the reaction, the color changes to yellow or orange (if the color remains red or dark red, add 0.6 g (9.1 mmol) of zinc powder). After changing the dichloromethane and H ₂ O, sulfate. The solvent was removed, and the product was recrystallized twice using ethyl alcohol to obtain 2 g (yield: 50%) of white DO-BDTO.

_{^{1 H-NMR (CDCl 3,}} 300 Mhz): δ (ppm) = 7.48 (d, 2H), 7.32 (d, 2H), 4.27 (t, 4H), 1.9 (m, 4H), 1.33 (m, 20H ), 0.9 (t, 6H)

Example 6 Synthesis of 2,6-Bis (trimethyltin) -4,8-dioctyloxybenzo [1,2-b: 4,5-b '] dithiophene (DT-BDT)

1 g (2.2 mmol) of DO-BDT is dissolved in 10 mL of THF and cooled to -78 ° C. 2.7 mL (6.7 mmol, 2.5 M) of n-BuLi is slowly added dropwise to the cooled DO-BDT and stirred for one hour. Add 6.7 mL (6.7 mmol, 1 M) of trimeyltin chloride, stir at -78 ° C for 30 minutes, raise to room temperature and incubate for 24 hours. Dichloromethane and H ₂ O were added and extracted. The organic layer was dried with magnesium sulfate, the solvent was removed, and recrystallization was performed twice with isopropanol to obtain 1.4 g (yield: 81%) of white DO-BDS.

¹ H-NMR (CDCl ₃ , 300 MHz):? (Ppm) = 7.51 (s, 2H), 4.3 (t, 4H), 1.9 (m, ), 0.4 (s, 18H)

Example 7 Synthesis of 2,5-Dibromo-3-hexylthiophene (DB-3HT)

3-Hexylthiophene (15 g, 89.1 mmol), acetic acid (180 mL) and n-bromosuccinimide (34.8 g, 196.0 mmol) were added and stirred for 30 minutes. Water was added and stirring was continued for 10 minutes. After extraction with ether and water, the organic layer was collected and the water was removed with MgSO ₄ to obtain a transparent liquid (21.0 g, yield: 75%).

_{^{1 H-NMR (CDCl 3,}} ppm): δ (ppm) = 7.17 (d, 1H), 6.80 (d, 1H), 2.59 (t, 2H), 1.60 (m, 2H), 1.35 (m, 10H) , 0.93 (t, 3H)

Example 8 Synthesis of 4-Bromo-benzyl thiol (4Br-BT)

Thiourea (7.8 g, 102 mmol) is dissolved in 50 mL of ethanol and heated. 4-bromo-benzyl chloride (20.5 g, 100 mmol) was added thereto and refluxed for 10 minutes. After removing the solvent of the solution, add 60 mL of the aqueous solution containing 7 g of NaOH and stir for one hour. After extraction with water, the organic layer was collected and the water was removed with MgSO ₄ to obtain a transparent liquid (11.8 g, yield: 95%).

_{^{1 H-NMR (CDCl 3,}} ppm): δ (ppm) = 7.44 (d, 2H), 7.21 (d, 2H), 3.69 (d, 2H), 1.75 (t, 1H)

Example 9: Synthesis of QD-P

0.3 g (0.39 mmol) of DO-BDS and 0.13 g (0.39 mmol) of DB-3HT are added and vacuum dried. After drying, add 15 mL of anhydrous toluene and stir for 30 minutes under an Ar stream. Put 0.04 g Pd (PPh ₃₎ a (0.04 mmol) ₄ to 24 hours at 120 ℃. After confirming the molecular weight by GPC, excess 4Br-BT is added to the reaction vessel and reacted for 12 hours. The reaction is terminated by reducing the temperature to room temperature and the catalyst is removed by short filtering with diatomaceous earth. The BT-P thus obtained is put into a vial at a ratio of 1: 3 (quantum dot: BT-P) to a quantum dot, dispersed in chloroform, and bound to the quantum dot through sonication.

Synthetic expression. Synthesis of QD-P

[Test Example]

Figure 2 shows HR-TEM images of the nanostructures prepared according to the embodiments of the present invention, wherein the diameter of the nanostructures of QD-P3000 was measured to be about 25 (± 5) nm and was distributed in a relatively similar size I could see that.

In FIG. 3, the FT-IR spectra of green QD and hybrid QD-P3000 nanoparticles coupled with oleic acid showed CS stretching peaks at 967 and 950 cm ^-1 . In addition, in the normalized UV-vis absorption spectrum of P3000 and QD-P3000 and the solution photoluminescence (PL) spectrum of green QD (see FIG. 4), the π- π * transition peak of P3000 was measured at 390 nm, It was visible at 460 nm. The absorption spectrum of QD-P3000 was somewhat milder than that of P3000, and the photoluminescence (PL) peak of green QD appeared at 530 nm. It can be seen that the emission spectrum of the green QD overlaps the absorption spectrum of the QD-P3000 nanostructure partially by about 26.7%, which is the energy transfer when the two systems are sufficiently close from the n-type QD to the p-type P3000, It can be foreseen that this will happen.

FIG. 5 shows a QD-P3000 nanostructure in which a P3000 organic semiconductor is bonded to the surface of a green light emitting CdSe / ZnS quantum dot by using a laser confocal microscope (LCM) light emission (PL) spectrophotometer to observe the nanoscale photoluminescence property . The QD-P3000 nanostructure showed a decrease in luminescence of QD-P3000 and a luminescence of P3000 in the QD-P3000 nanostructure.

Figure 6 shows transient absorption (time-resolved absorption) spectra of each nanostructure at laser pumping after laser pumping at a wavelength of 510 nm from which the quantum dot conjugated molecules Hybridization.

Exciton lifetime was determined by the normalized time-resolved photoluminescence (PL) decay curve (see FIG. 7) of the green QD and QD-P3000 nanostructures. In QD-P3000, it was confirmed that the exciton lifetime shortens sharply due to the charge transfer phenomenon.

Also, it can be seen that the charge transfer is occurring well in the nanostructure through the photocurrent current-voltage characteristic curve (see FIG. 8) using the conductive atomic force microscope and the laser (λ _ex = 488 nm) of the QD-P3000 single nanostructure there was. Especially, increase of photocurrent due to external light application is observed, and it is possible to apply it as photovoltaic characteristic material for development of nano solar cell.

Claims (17)

A core layer made of quantum dots;
A shell layer made of an organic semiconductor compound having a pi-conjugated structure;
≪ / RTI >
The quantum dot of claim 1, wherein the quantum dot is a combination of two selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgTe, GaN, GaP, GaAs, InP, Nano structure
3. The nanostructure according to claim 2, wherein the quantum dot is selected from the group consisting of CdSe / ZnS, CdSe / ZnSe, CdS / ZnSe, CdS / ZnS, CdTe / ZnSe,
2. The nanostructure according to claim 1, wherein the organic semiconductor compound is a compound represented by the following formula (1)
≪ Formula 1 >

(In the formula 1,

Wherein R represents a core layer, R is C1-C20 alkyl optionally substituted with a substituent, C2-20 alkenyl optionally substituted with a substituent, C2-20 alkynyl optionally substituted with a substituent, An unsubstituted C1-20 alkoxy group or an unsubstituted C6-30 aryloxy group, and the substituent is selected from the group consisting of C1-C20 alkyl, halogen, C1-C20 alkoxy, OH, deuterium And n represents an integer of 1 to 20,
5. The nanostructure according to claim 4, wherein the nanostructure has a diameter of 30 to 20 nm
The nanostructure according to claim 5, wherein the nanostructure is an np junction type
The organic semiconductor compound according to claim 4, wherein the organic semiconductor compound is a compound represented by Formula 1 wherein R is C1-C20 alkyl.
The organic semiconductor compound according to claim 4, wherein the organic semiconductor compound is a compound represented by Formula 1 wherein R is C5-C10 alkyl.
The method of claim 4, wherein the quantum dots are nanostructures, characterized in that R is C ₈ H ₁₇ in the compound comprise a CdSe / ZnS represented by the organic semiconductor compound is <Formula 1> compound
A molecular electronic device comprising a nanostructure according to any one of claims 1 to 9 between a first pole and a second pole.
An electronic device comprising a molecular electronic device comprising a nanostructure according to any one of claims 1 to 9
The electronic device according to claim 11, comprising a solar cell, a display or a lighting device including the molecular electronic device, and a control unit controlling the same
A compound represented by the following formula (2)
(2)

(Wherein R and n are the same as defined in claim 4)
14. The compound according to claim 13, wherein R is a compound represented by C8H17
a) fabricating core-shell quantum dots with two inorganic semiconductor materials;
b) chemically synthesizing the P-type conjugated organic semiconductor compound;
c) introducing a functional group into the terminal of the organic semiconductor compound;
d) introducing the compound into a surface of a quantum dot, wherein the quantum dot and the organic semiconductor compound are in the form of a core-shell layer.
The method according to claim 15, wherein the compound in step (c) is a compound represented by the following formula (2)
(2)

[17] The method according to claim 16, wherein the step (d) comprises introducing a compound represented by Formula 2 into a quantum dot by an ultrasonic wave in a ligand exchange manner

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